[mapserver-users] Rendering weather data

[Brent Fraser]

Norman,

   Many thanks for the link; it's good to see how others have approached 
the problem.  The font referenced is an ESRI font so I don't think I can 
use it due to copyright, but perhaps I could construct my own using the 
same glyph indexes for compatibility.

Best Regards,
Brent Fraser


On 9/27/2011 12:09 PM, Norman Vine wrote:
>
> On Sep 27, 2011, at 2:03 PM, Paul Ramsey wrote:
>
>> Once you have vectors, the classic trick I've seen for doing the barbs
>> is to do math to map the windspeed into an appropriate char() value
>> and store the barbs as TTF font entries. So you only end up with one
>> class, and the barb is an appropriately rotated label.
>
> This might help
> http://carocoops.org/bb/viewtopic.php?t=169
>
>
>>
>> P.
>>
>> On Tue, Sep 27, 2011 at 10:31 AM, Brent Fraser 
>> <bfraser at geoanalytic.com <mailto:bfraser at geoanalytic.com>> wrote:
>>>    At FOSS4G I was struck by the number of presentations involving 
>>> weather
>>> data and time series display.  Maybe I noticed because I have a need to
>>> render wind velocity in KML, and while I haven't settled on 
>>> mapserver to do
>>> the rendering I've been wondering how to render wind barb symbols (see
>>> attached graphics) efficiently.
>>>
>>>  One problem is the source data: the magnitude is in one raster file 
>>> (GRIB
>>> format, float64)  and the direction in another.  GDAL's OGR library will
>>> read the GRIB files, but I don't know of any way to use two rasters to
>>> define a vector layer.  I think there is some work going on with 
>>> respect to
>>> displaying vector field data in mapserver, so maybe this will be 
>>> solved by
>>> that work.  Otherwise pre-processing the two rasters into a point 
>>> datasource
>>> containing lon,lat,speed,direction attributes may be the way to go.
>>>
>>>  The other issue of wind barb symbol rendering may have to be solved 
>>> by hand
>>> constructing a barb for 0 knots, 5 knots, etc (50-ish symbols?) , 
>>> and having
>>> 50-ish corresponding classes (this could be a performance problem for
>>> mapserver).  But I'm open to better ideas...  SLD?  HTTP/CGI request?,
>>> something like one class of:
>>>
>>>  CLASS
>>>    STYLE
>>>      GEOMTRANSFORM "start"
>>>      COLOR 0 255 0
>>>      SIZE 15.0
>>>      SYMBOL "http://localhost/symbolgen?[speed]"
>>>      ANGLE [direction]
>>>    END
>>>  END
>>>
>>>  but likely the cost of getting the symbol would be greater that 
>>> creating 50
>>> separate class objects.
>>>
>>> And for those interested in mapping and graphing weather data, have 
>>> a look
>>> at http://www.ncl.ucar.edu/Applications/
>>> especially http://www.ncl.ucar.edu/Applications/barb.shtml
>>>
>>> --
>>> Best Regards,
>>> Brent Fraser
>>>
>>>
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